Hi, Karen,
In my former salt mine, where we used organic boards, it was standard
practice to bake the bare boards for 2 hours at 90 deg C to drive off
absorbed moisture prior to assembly. Thereafter, the boards were kept in
low humidity or nitrogen cabinets between assembly operations until after
conformal coating.
How are your boards packed when they arrive with you from the
manufacturer? I would expect them to be in sealed bags with desiccant, and
they should be left that way (or resealed immediately after inspection in
vacuum bags with desiccant) until you're ready to assemble them,
preferrably in the low humidity cabinet. How long are you leaving the
boards on the shop floor after baking? You should try and arrange matters
so that they're not baked until they're required, and thereafter used
immediately.
Regards
Pete Duncan
Karen Walters
<KWalters@BTU To: [log in to unmask]
.COM> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Sent by: Subject: [TN] PCB Moisture Absorption
TechNet
<[log in to unmask]
ORG>
08/09/01
02:39 AM
Please
respond to
"TechNet
E-Mail
Forum.";
Please
respond to
Karen Walters
I am trying to solve the problem of cracking inside a printed
circuit board due to moisture absorption, temperature in the oven and the
thermal gradient observed on the board. After the drying process, the
boards are left outside
in the manufacturing area, but due to the environment they are absorbing
moisture again. I would like to know which products would fit
better(sealed
bags,vacuum bag,with/without desiccant,low humidity or nitrogen filled
storage cabinets...). Also has anyone done a study on moisture absorption
in a PCB under different environment conditions, and baking requirements
for
different environmental conditions?
If you have any data, please advise.
**********************************************************************
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom they
are addressed. If you have received this email in error please notify
the system manager at [log in to unmask]
**********************************************************************
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET
Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
---------------------------------------------------------------------------------
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------
|
